前言

本文介绍milkv-duo加载st7735的lcd屏幕，以及屏幕显示log。

参考文章：
记录为Linux配置spi屏幕（st7735s）
https://community.milkv.io/t/milk-v-duo-spi-st7789/131

一、电路图

1.1 pin设置

打开spi2的引脚
duo-buildroot-sdk\build\boards\cv180x\cv1800b_milkv_duo_sd\u-boot\cvi_board_init.c

	//spi2 -- st7735pinmux_config(PINMUX_SPI2);PINMUX_CONFIG(SPINOR_MISO, XGPIOA_23);	//DCPINMUX_CONFIG(SD0_PWR_EN, XGPIOA_14);	//BLPINMUX_CONFIG(SPK_EN, XGPIOA_15);		//RES

注意这里的DC，属于gpioA

这里的pinmux_config(PINMUX_SPI2);可以在源码中找到对应的配置

		case PINMUX_SPI2:PINMUX_CONFIG(SD1_CMD, SPI2_SDO);PINMUX_CONFIG(SD1_CLK, SPI2_SCK);PINMUX_CONFIG(SD1_D0, SPI2_SDI);PINMUX_CONFIG(SD1_D3, SPI2_CS_X);break;

1.2 dtsi配置

build\boards\cv180x\cv1800b_milkv_duo_sd\dts_riscv\cv1800b_milkv_duo_sd.dts

&spi2 {status = "okay";/delete-node/ spidev@0;st7789v: st7789v@0{compatible = "sitronix,st7789v";reg = <0>;status = "okay";spi-max-frequency = <48000000>;spi-cpol;spi-cpha;rotate = <90>;fps = <30>;rgb;buswidth = <8>;dc-gpios = <&porta 23 GPIO_ACTIVE_HIGH>;	//DCreset-gpios = <&porta 15 GPIO_ACTIVE_HIGH>; //RESled-gpios = <&porta 14 GPIO_ACTIVE_HIGH>; //BLdebug = <0x0>;};
};

这里的gpio要结合你的引脚实现。

二、加载驱动

仿照参考文章，使用st7789v代码改动到st7735上。
记录为Linux配置spi屏幕（st7735s）

编译条件
duo-buildroot-sdk\linux_5.10\drivers\staging\fbtft\Makefile

obj-$(CONFIG_FB_TFT_ST7735R)     += fb_st7735r.o
obj-$(CONFIG_FB_TFT_ST7789V)     += fb_st7789v.o

借用st7789v的代码

st7735s和st7735r一致

引用：https://www.cnblogs.com/milton/p/15614304.html#St7735%E4%BB%8B%E7%BB%8D 
ST7735的配置
因为ST7735存在多个型号, 对于ST7735R和ST7735S, 使用默认的初始化方法

duo-buildroot-sdk\build\boards\cv180x\cv1800b_milkv_duo_sd\linux\ cvitek_cv1800b_milkv_duo_sd_defconfig

# spi lcd -- st7735s
CONFIG_SPI=y
CONFIG_SPI_MASTER=y
CONFIG_SPI_DESIGNWARE=y
CONFIG_SPI_DW_MMIO=y
CONFIG_SPI_SPIDEV=y
CONFIG_FB=y
CONFIG_FB_TFT=y
# CONFIG_FB_TFT_ST7735R=y
CONFIG_FB_TFT_ST7789V=y

编译过程提示

  CC      drivers/staging/fbtft/fb_st7789v.o

三、更改驱动

3.1 st7789v驱动

duo-buildroot-sdk\linux_5.10\drivers\staging\fbtft\fb_st7789v.c

参考来源：https://blog.csdn.net/qq_46604211/article/details/116449891

3.1.2 接口更新

由于驱动是st7789v，我的屏幕是st7735，需要更改一些初始化接口。

注意gamma需要注释掉for循环。

// st7735
static int init_display(struct fbtft_par *par)
{par->fbtftops.reset(par);//硬复位mdelay(50);write_reg(par,0x11);//软复位mdelay(100);//下面添加初始化函数write_reg 参数分别为：结构体指针，写命令，写数据....(后都为数据)//ST7735s Frame Ratewrite_reg(par,0xB1,0x05,0x3c,0x3c); write_reg(par,0xB2,0x05,0x3c,0x3c);  write_reg(par,0xB3,0x05,0x3c,0x3c,0x05,0x3c,0x3c); write_reg(par,0xB4,0x03); //Column inversion //ST7735s Power Sequencewrite_reg(par,0xC0,0x28,0x08,0x04); write_reg(par,0xC1,0xc0); write_reg(par,0xC2,0x0d,0x00); write_reg(par,0xC3,0x8d,0x2a); //VCOM write_reg(par,0xc4,0x8d,0xee); //MX, MY, RGB mode  write_reg(par,0xc5,0x1a);write_reg(par,0x36,0xc0);//ST7735s Gamma Sequencewrite_reg(par,0xe0,0x04,0x22,0x07,0x0a,0x2e,0x30,0x25,0x2a,0x28,0x26,0x2e,0x3a,0x00,0x01,0x03,0x13); write_reg(par,0xe1,0x04,0x16,0x06,0x0d,0x2d,0x26,0x23,0x27,0x27,0x25,0x2d,0x3b,0x00,0x01,0x04,0x13);  write_reg(par,0x3A,0x05); //65k mode  write_reg(par,0x29);//Display onmdelay(100);return 0;
}static int set_gamma(struct fbtft_par *par, u32 *curves)
{int i;int j;int c; /* curve index offset *//** Bitmasks for gamma curve command parameters.* The masks are the same for both positive and negative voltage* gamma curves.*/static const u8 gamma_par_mask[] = {0xFF, /* V63[3:0], V0[3:0]*/0x3F, /* V1[5:0] */0x3F, /* V2[5:0] */0x1F, /* V4[4:0] */0x1F, /* V6[4:0] */0x3F, /* J0[1:0], V13[3:0] */0x7F, /* V20[6:0] */0x77, /* V36[2:0], V27[2:0] */0x7F, /* V43[6:0] */0x3F, /* J1[1:0], V50[3:0] */0x1F, /* V57[4:0] */0x1F, /* V59[4:0] */0x3F, /* V61[5:0] */0x3F, /* V62[5:0] */};for (i = 0; i < par->gamma.num_curves; i++) {c = i * par->gamma.num_values;// for (j = 0; j < par->gamma.num_values; j++)// 	curves[c + j] &= gamma_par_mask[j];write_reg(par, PVGAMCTRL + i,curves[c + 0],  curves[c + 1],  curves[c + 2],curves[c + 3],  curves[c + 4],  curves[c + 5],curves[c + 6],  curves[c + 7],  curves[c + 8],curves[c + 9],  curves[c + 10], curves[c + 11],curves[c + 12], curves[c + 13]);}return 0;
}

3.1.3 更改宽高

st7735的屏幕宽高为128*160。

duo-buildroot-sdk\linux_5.10\drivers\staging\fbtft\fb_st7789v.c

static struct fbtft_display display = {.regwidth = 8,.width = 128,//240,.height = 160,//320,.gamma_num = 2,.gamma_len = 14,.gamma = HSD20_IPS_GAMMA,.fbtftops = {.init_display = init_display,.set_var = set_var,.set_gamma = set_gamma,.blank = blank,},
};

3.2 fbtft-core

duo-buildroot-sdk\linux_5.10\drivers\staging\fbtft\fbtft-core.c

3.2.1增加头文件

#include <linux/gpio.h> //add
#include <linux/of_gpio.h> //add

3.2.2 更改接口

这是由于内核版本更新导致的，一些接口可能需要改动。
dtsi中的属性加上-gpio可以自行选择。
reset重新实现。

//https://blog.csdn.net/qq_46604211/article/details/116449891
static int fbtft_request_one_gpio(struct fbtft_par *par,const char *name, int index,struct gpio_desc **gpiop)
{struct device *dev = par->info->device;struct device_node *node = dev->of_node;int gpio, flags, ret = 0;enum of_gpio_flags of_flags;if (of_find_property(node, name, NULL)) {gpio = of_get_named_gpio_flags(node, name, index, &of_flags);if (gpio == -ENOENT)return 0;if (gpio == -EPROBE_DEFER)return gpio;if (gpio < 0) {dev_err(dev,"failed to get '%s' from DT\n", name);return gpio;}//active low translates to initially lowflags = (of_flags & OF_GPIO_ACTIVE_LOW) ? GPIOF_OUT_INIT_LOW :GPIOF_OUT_INIT_HIGH;ret = devm_gpio_request_one(dev, gpio, flags,dev->driver->name);if (ret) {dev_err(dev,"gpio_request_one('%s'=%d) failed with %d\n",name, gpio, ret);return ret;}*gpiop = gpio_to_desc(gpio);fbtft_par_dbg(DEBUG_REQUEST_GPIOS, par, "%s: '%s' = GPIO%d\n",__func__, name, gpio);}return ret;
}static int fbtft_request_gpios(struct fbtft_par *par)
{int i;int ret;ret = fbtft_request_one_gpio(par, "reset-gpios", 0, &par->gpio.reset);if (ret)return ret;ret = fbtft_request_one_gpio(par, "dc-gpios", 0, &par->gpio.dc);if (ret)return ret;ret = fbtft_request_one_gpio(par, "rd-gpios", 0, &par->gpio.rd);if (ret)return ret;ret = fbtft_request_one_gpio(par, "wr-gpios", 0, &par->gpio.wr);if (ret)return ret;ret = fbtft_request_one_gpio(par, "cs-gpios", 0, &par->gpio.cs);if (ret)return ret;ret = fbtft_request_one_gpio(par, "latch-gpios", 0, &par->gpio.latch);if (ret)return ret;for (i = 0; i < 16; i++) {ret = fbtft_request_one_gpio(par, "db-gpios", i,&par->gpio.db[i]);if (ret)return ret;ret = fbtft_request_one_gpio(par, "led-gpios", i,&par->gpio.led[i]);if (ret)return ret;ret = fbtft_request_one_gpio(par, "aux-gpios", i,&par->gpio.aux[i]);if (ret)return ret;}return 0;
}//作者：Leesans https://www.bilibili.com/read/cv9947785/ 出处：bilibili
static void fbtft_reset(struct fbtft_par *par)
{if (!par->gpio.reset)return;fbtft_par_dbg(DEBUG_RESET, par, "%s()\n", __func__);gpiod_set_value_cansleep(par->gpio.reset, 1);msleep(10);gpiod_set_value_cansleep(par->gpio.reset, 0);msleep(200);gpiod_set_value_cansleep(par->gpio.reset, 1);msleep(10);
}

四、屏幕显示结果

驱动正常加载。

通过如下两个命令可以测试屏幕功能。

cat /dev/urandom > /dev/fb0 	//显示花屏
cat /dev/zero > /dev/fb0  		//清空屏幕
echo xxxx > /dev/fb0 				//显示点个数

仔细看右上角，有一条颜色不同的线，很短，你可以echo后面跟很长的x，x越多，线越长。
这是手动赋值给像素点的。

五、用屏幕显示log

参考来源：
https://community.milkv.io/t/milk-v-duo-spi-st7789/131

5.1 添加编译模块

duo-buildroot-sdk\build\boards\cv180x\cv1800b_milkv_duo_sd\linux\cvitek_cv1800b_milkv_duo_sd_defconfig

# lcd display kernel log
CONFIG_TTY=y
CONFIG_VT=y
CONFIG_CONSOLE_TRANSLATIONS=y
CONFIG_VT_CONSOLE=y
CONFIG_HW_CONSOLE=y
CONFIG_VT_HW_CONSOLE_BINDING=y
CONFIG_FB=y
CONFIG_FB_CMDLINE=y
CONFIG_FB_NOTIFY=y
CONFIG_FONT_SUPPORT=y
CONFIG_FONTS=y
CONFIG_FONT_8x16=y
CONFIG_VGA_CONSOLE=y
CONFIG_DUMMY_CONSOLE=y
CONFIG_DUMMY_CONSOLE_COLUMNS=80
CONFIG_DUMMY_CONSOLE_ROWS=25
CONFIG_FRAMEBUFFER_CONSOLE=y
CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY=y

5.2 添加tty0用于显示log

duo-buildroot-sdk\u-boot-2021.10\include\configs\cv180x-asic.h

#define SET_BOOTARGS "setenv bootargs ${root} ${mtdparts} " \"console=tty0 console=$consoledev,$baudrate $othbootargs;"

5.3 显示